Several heretofore untried approaches to the preparation of macromolecular conjugates of antitumor agets will be investigated with a view to achieving a high "drug load. 5-Fluoro-2'-deoxyuridine (FUdR) and methotrexate (MTX) will be used as ligands, with poly-L-lysine comprising the carrier. Suitable protected derivatives of the NAlpha-carboxyanhydrides of L-lysine and N Epsilon -(FUdR 5'-o-CO(CH2)xCO)-L-lysine will be copolymerized and deblocked to give products which are expected to have FUdR content per unit weight than is possible to obrtain by direct coupling of FUdR 5' -O-hemiesters to pre-formed poly-L-lysine. A second strategy is also proposed, in which the essential element will involve peptides of the type N Epsilon-(FUdR 5'-O-CO(CH2)xCO)-L-lysyl-(NAlpha-lysyl)n-L-lysine with the Epsilon-amino groups of the oligo-L-lysine moiety blocked and the Alpha-carboxyl group of the C-terminal lysine residue activated as an N-hydroxy succinimide ester. Spontaneous polymerization of these activated peptides in DMF solution followed by deblocking should yield products in which the FUdR/lysine ratio directly reflects n. A similar approach will be followed in order to prepare MTX-poly(L-lysine) with a higher MTX content than is achievable by direct carbodiimide coupling of MTX to poly-L-lysine. FUdR and MTX conjugates generated via these methods will be subjected to HPLC bio-analytical studies in mice to evaluate their ability to act as sustained-release drug delivery systems. As sufficient amounts of material bbbbbcome available, antitumor assays in mice will likewise be carried out.